As the king's captain, Gideon heard these things because he was probably assigned to make the search. This indication of Gideon's formal position with Limhi reinforces the suggestion that he was similarly powerful under the reign of Noah. At this point Gideon does not know that the priests have stolen the daughters of the Lamanites, but as the captain of a military guard that was probably guarding the city in case of Lamanite attack, he should have been aware of any outgoing group, and particularly any group of people returning with unknown women (who would probably have made known their involuntary participation). When we remember that the entire city was vigilant, as suggested by Limhi's discovery of the Lamanite preparations, it would make sense that while Gideon could not prove that it was the priests, he would have known that it was not the current people of Limhi.